#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
//
// Copyright (c) 2005-2009 empira Software GmbH, Cologne (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using PdfSharp.Drawing;
using PdfSharp.Internal;

using Fixed = System.Int32;
using FWord = System.Int16;
using UFWord = System.UInt16;

namespace PdfSharp.Fonts.OpenType
{
  /// <summary>
  /// Base class for all OpenType fonts.
  /// </summary>
  internal class OpenTypeFontTable : ICloneable
  {
    public OpenTypeFontTable(FontData fontData, string tag)
    {
      this.fontData = fontData;
      if (fontData != null && fontData.tableDictionary.ContainsKey(tag))
        this.DirectoryEntry = fontData.tableDictionary[tag];
      else
        this.DirectoryEntry = new TableDirectoryEntry(tag);
      this.DirectoryEntry.FontTable = this;
    }

    /// <summary>
    /// Creates a deep copy of the current instance.
    /// </summary>
    public object Clone()
    {
      return DeepCopy();
    }

    protected virtual OpenTypeFontTable DeepCopy()
    {
      OpenTypeFontTable fontTable = (OpenTypeFontTable)MemberwiseClone();
      fontTable.DirectoryEntry.Offset = 0;
      fontTable.DirectoryEntry.FontTable = fontTable;
      return fontTable;
    }

    /// <summary>
    /// Gets the font image the table belongs to.
    /// </summary>
    public FontData FontData
    {
      get { return this.fontData; }
    }
    internal FontData fontData;

    public TableDirectoryEntry DirectoryEntry;

    /// <summary>
    /// When overridden in a derived class, prepares the font table to be compiled into its binary representation.
    /// </summary>
    public virtual void PrepareForCompilation()
    {
    }

    /// <summary>
    /// When overridden in a derived class, converts the font into its binary representation.
    /// </summary>
    public virtual void Write(OpenTypeFontWriter writer)
    {
    }

    /// <summary>
    /// Calculates the checksum of a table represented by its bytes.
    /// </summary>
    public static uint CalcChecksum(byte[] bytes)
    {
      Debug.Assert((bytes.Length & 3) == 0);
      // Cannot use Buffer.BlockCopy because 32-bit values are Big-endian
      uint byte3, byte2, byte1, byte0;
      byte3 = byte2 = byte1 = byte0 = 0;
      int length = bytes.Length;
      for (int idx = 0; idx < length;)
      {
        byte3 += bytes[idx++];
        byte2 += bytes[idx++];
        byte1 += bytes[idx++];
        byte0 += bytes[idx++];
      }
      return (byte3 << 24) + (byte2 << 16) + (byte1 << 8) + byte0;
    }
  }
}
